This 35 second animation illustrates the Meridional Overturning Circulation (MOC) of the global oceans.

The actual circulation may require anywhere from centuries to millenia to complete one global cycle.

GIF animation showing MOC

Warm water near the surface of the ocean is shown in red. As the warm water moves poleward, it is cooled and sinks to become the deep water, shown in blue. Intermediate temperature, near-surface water is shown in yellow.